Telephone system



Feb. 27, 1940. J, usc 2,192,025

TELEPHONE SYSTEM Filed June 17, 1938 9 Sheets-Sheet 1 A T TOR/V5 V QNNFeb. 27, 1940.

O 2. I INVENTOR By AJBUSCH A. J. BUSCH TELEPHONE SYSTEM File d June 17.1938 Feb. 21, 1940..

9 Sheets-Sheet 3 INVENTOR AJBUSCH BY A T TORNE V Feb. 27, 1940. A. J.BUSCH TELEPHONE SYSTEM 9 Sheets-Sheet 4 Filed June 17. 1938 lNl/ENTOR A.J. BUSCH By W A 7' TORNE V Feb. 27, 1940. A. J. BUSCH 2,192,025

TELEPHONE SYSTEM Filed June 17, 19:53 9'SheetsSheet s //v l/EA/ TOR ByAJ. BUSCH A T TORNE V Feb. 27, 1940.

A. J. BUSCH 2,192,025

TELEPHONE SYSTEM Filed June 17, 1938 9 Sheets-Sheet 6 FIG. 6

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wwww ATTORNEY Feb. 27, 1940. A. J. BUSCH 2,192,025

TELEPHONE SYSTEM Filed June 17. 1938 9 Sheets-Sheet '7 //v ve/v TOR B yAJ. BUSCH WWW ATTORNEY Feb. 27,1940. A. J. BUSCH TELEPHONE SYSTEM FiladJune 17, 1938 9 Sheets-Sheet 8 VI mm T5 0 NU q .T we w r W H W. A

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A. J. BUSCH mmarnoufi SYSTEM Imam Jun'e'17, 1938 9 Shoetg-Sheet 9lA/VENTOR AJ. BUS CH WSW'JM ATTORNEY Patented Feb. 27, 1940 PATENTOFFICE TELEPHONE SYSTEM Aloysius J. Busch, Madison, N. J assignor toBell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application June 1'7, 1938,Serial No. 214,348

10 Claims.

This invention relates to telephone "systems and particularly to systemsin which automatic.

switching equipment is employed for establishing connections.

It has been the practice heretofore in automatic telephone systems toprovide common controlling mechanisms at the central officefor thepurpose of collecting at periodic intervals during a telephoneconversation the coins that are deposited by the calling party at a coinsubrstation. Since these controlling mechanisms are common to a numberof trunk circuits in the central ofiice, and since their service isrequired only for a short interval of time while the deposited coin isbeing collected,.the usual arrangement is to connect an 'idle one ofthese mechanisms to any one of the trunks having a call thereon whichhas progressed to the point where the deposited. coin should becollected and thereafter to restore the mechanism to normal in orderthat it may be taken in use by any other trunk having a call thereonthat requires similar treatment. In addition to these periodic coincollecting operations it is also the practice in systems of this kind tomake tests of the calling coinline at regular intervals to determinethat the calling patron has deposited a coin entitling him to anotherinterval of conversation. In the past, the'testing devices'for testingthe calling line to determine whether the coin has been deposited havebeen associated individually with the trunk circuits over which theconversational connections are established. Moreover, it has beennecessary to provide individual connecting circuits, such as operatorsjacks, for each of the trunk. circuits in order that a monitoringoperator could make connection with any one of the trunks having a callthereon in the: event that the testing mechanism discovers that thecalling patron has failed to deposit a coin for the next periodicinterval of conversation.

The objects of the present invention are to simplify the equipment usedin these systems by combining in a single controlling mechanism thefunction of testing for a depositedcoin and the function of disposing ofthe coin; to obtain a more reliable test for the presence of the coinsdeposited by the calling patron;v to simplify the equipment necessaryfor monitoring on the established connections; and to secure otherimprovements in systems of this general character.

A feature of the present invention is a system in which a plurality ofcoin-control mechanisms are provided in common to the conversationaltrunks in the central office, and in which any particular one of thetrunks having a call thereon, establishedfrom a coin substation, seizesan idle one of the control mechanisms for a brief interval near the endof each overtime period of conversation and again seizes an idle one ofthese mechanisms for a brief interval at the end of each such overtimeperiod. When the control mechanism is connected to the trunk near theexpiration of the conversational period,

it proceeds to collect the coin that was previously deposited at thecalling substation in payment for the: conversational period. At thistime the control mechanism also transmits a warning tone to the callingparty, advising him that the conversational period is about to expireand that he should deposit a new coin if he wishes to continue. I On itssubsequent connection to the conversational circuit, namely, at the endof the full conversational period, the control mechanism makes a test ofthe calling line to determine whether the calling party has deposited anew coin for the next period. If the mechanism fails to find'the coinwhen it attempts to collect on itsfirst association with the circuitmonitoring operator is" signaled and shemakes connection with thecalling line, by way of a deposits the new coin or advises the operatorthat he has already done so, she withdraws from the connection.

Another feature of the invention is an arrangement whereby the controlmechanism makes a retest of the calling line for the presence of a coinafter the monitoring operator withdraws from the connection followingher request to the calling party to deposit a new coin for the nextconversational period.

the mechanism is disconnected and returns to common use; but, if theretest shows no coin is present, the mechanism again signals the monitoring operator, and she returns to the con- If on retest the controlmechanism finds that a coin has been deposited,

near the end of the conversational period, the

While the system .disclosed is not limited to the nection and requeststhe calling party to deposit the coin. And on each withdrawal of themonitoring operator the control mechanism tests the line for thepresence of the coin and will not retire from the connection until thistest has been satisfied.

A further feature of the invention is the provision whereby themonitoring operator obtains connection to any calling coin line by meansof connecting circuits, such as jacks, which are individual to thecommon control mechanisms. The control mechanism is always associatedwith the individual subscribers line at the time the monitoringoperators service is required, and by giving her access to the lines byway of these common mechanisms rather than by way of connecting circuitsindividualto the central oflice trunks, a considerable economy iseffected in the equipment required, and a concentration of the operatorsconnecting circuits is also obtained.

These and other features of the invention will be discussed more fullyin detail in the following description and will also be set forth in theappended claims.

Referring to the drawings which accompany the detailed specification:

Fig. 1 shows a district junctor circuit arranged to function with acoini-control circuit and connected conventionally with a coin-boxsubscriber station by a line link and group control circuit Fig. 5 is anabridged form of a link and control circuit to illustrate means wherebya connection between the district junctor of Fig. 1 and the coin-controlcircuit of Figs. 6, 7 and 8 may be established;

Figs. 6, '7 and 8 placed together in order from left to right illustratethe coin-control circuit; arranged according to this invention;

Fig. 9 illustrates in an abbreviated schematic manner the connection ofthe district junctor of Fig. 1 through a subscriber sender link andcontrol circuit to a subscriber sender circuit, conventionallyrepresented by a box; and

Fig. 10 is a block diagram showing the manner in which the severalfigures of the drawings, should be arranged to show a complete system.

General description The invention is illustrated in an automatictelephone system in which automatic switches of the cross-bar type areused as the medium for extending connections from subscribers lines overtrunks to other subscribers lines. These cross-bar switching mechanismsare controlled by register senders at the central office, which receivethe designations from the calling subscribers dials, and by decodermarkers. These markers are connectable to the senders for receivinginformation from the senders and are connectable to the proper switchframes for the purpose of testing the outgoing trunks and for testingthe connecting links and for operating the magnets of the cross-barswitches to establish the connections.

use of cross-bar switches of any particular type, reference may be hadto the patent to Reynolds 2,021,329 of November 19, 1935, for anunderstanding of the construction and operation of a switch suitable foruse in such systems. Because .of. the complicatednature of thesesystems, and

will be understood that the circuits and equip- Y ment so referred toare already known and in particular reference is here made to thefollowing for a detailed disclosure of operations and equipment referredto herein but not specifically dis- 14, 1937; and Carpenter applicationSerial No. 214,356, filed June 17, 1938.

The subscribers lines, such as line I00, are

connected to verticals of the primary cross-barswitches indicatedconventionally by theappa-- ratus in the box I01 and thence extendedthrough secondary switches, suchas switch I02, to district junctorcircuits; The'connections to the district junctor circuits are effectedby means of a line link and group control circuit and a subscribersender link and control circuit. The circuit'details (not shown) wherebythese connections ,to'

the district junctor circuits are effected may be the same as inCarpenter Patent 2,093,117, and

Carpenter application Serial No. 214,356, above,

mentioned. I

When the connection to the district junctor, which is one of a group ofsimilar junctors, not

shown, is established as above outlined, the sube scriber sender 900,througha link circuit represented in abbreviated form by primary andsec-5 ondary cross-bar switches 90! and 902, functions in associationwith a marker circuit, indicated by,

a box 200, to establish connection to an outgoing trunk 206, inaccordance with the office code dialed at calling station 103 andrecorded by sender, 900. through district framejcross-bar switches 20!and 202 and office frame switches 203 and 204.

When the outgoing trunk206 is thus seized a connection is establishedthrough an incoming,

link and connector circuit consisting of cross-bar switches 300 and 30l, and line link circuit consisting of cross-bar switches 302 and 303,to thelineof the called subscriber station 304. After the subscriber ofstation 304 answers, this condition is registered in the districtjunctor of Fig. 1.

The district junctor of Fig. 1 has common ac cess to a groupofcoin-control circuits, one of which is shown by Figs. 6, '7 and 8.nection to a selected coin-control circuit is made by means of the linkand control circuit of Fig. 5, which consists essentially of primaryandsecondary cross-bar switches 500 and 50]. This link and the associatedcontrol circuit, whereby a calling district junctor is connected to an.idle coin control circuit, are not shown in full detail since they arewell known and may be essensentially the same as those shown inCarpenter Patent 2,093,117, and Carpenter application Serial No.214,356, above mentioned.

This connection. is established. Y

The con- The district junctor circuit of Fig. l is arranged 2o closed:Carpenter Patent 2,093,117 of September 5 lay I12 to ground on conductorH6.

after a completed connection, immediately after the calling party'hasdisconnected; (b) to collect a coin-during conversation at the end of apredetermined interval; (0) to return a coin after an incompletedconnection immediately after the calling party disconnects or for a freecall; (0K) to test for the presence of an additional coin at thebeginning of an overtime period, and, in

case no coin is found, to summon an operator for overtime monitoring onthe connection. In the case of condition (a), before mentioned, the coincontrol circuit makes a test to determine the presence or non-presenceof a coin in the coin box I04 and to determine whether or not the coinbox "14 has been properly cleared after the application of coin-collectcurrent. For either of these conditions lamp 8% is flashed to inform anoperator of the failure to collect the coin. For condition (1)), shouldthe coin-control circuit fail to find a coin, lamp 8M is immediatelyflashed to inform the operator of this condition. For con dition (c),lamp 880 is lighted steadily if the coin box is not properly clearedafter the application of coin return current. For condition (d), theoperator is summoned by the steady lighting of lamp 8M, if the testindicates no coin is present.

Detailed description of operation The operation of the system will nowbe described in detail, and for this purpose let it be assumed that thecalling party or" station H33 initiates a call by depositing a coin I05in coin box I04 and by actuating the telephone switch of station I03. Acircuit is thereby closed for operating line relay Iilt, whichcircuitmay be traced from battery through the winding of relay I06, lowermostcontacts of cross-bar switch hold magnet Hll, over ring conductor ofline Iiiil, through the switch contacts of station I03 and thewind ingand associated contacts I68 of coin collector magnet I68 to ground Hi9.Line relay I06 functions in cooperation with the line link and groupcontrol circuit of Fig. 1 and the subscriber sender link and control andsubscriber sender circuits of Fig. 9 to effect the selection of an idledistrict junctor circuit, and an idle line link extending thereto. Theidle condition of the district junctor circuit is indicated by thepresence of battery on busy test lead I I3. The circuit details, wherebythis is accomplished are shown by the aforesaid patent application of W.'W. Carpenter, Serial No. 214,356, filed June 1'7, 1938. l

The selection before stated having been made, cross-bar switch contactsof the primary switch NH, and of the secondary switch Hi2, are closed,extending the conductors of line Mil to conductors I I0 and l I I, whichterminate respectively on the upper outermost, and lower innermost breakcontacts of relay H2, through which contacts connection is made overconductors IM and H5,

through the cross-bar switch contacts of the agramatically by boxes tilland SE32, to subscriber sender Silil. Dial tone is now furnished overthese conductors as an indication to the party of station I03 thatdialing may now bestarted. Ground is also connected at this time by thehold magnet 994 of the subscriber sender link and control circuit toconductor H6 and thereby is operated relay H1. The operating circuit maybetraced from battery through the winding of relay Ill, uppernext-to-innermcst break contacts of re- Relay H1 in operating performsnouseful function at this time, except to disconnect busy test battery H8from test conductor i I3, this circuit being traced from battery H8,through resistance H9, upper outermost break contacts of relays I20 andIZI, and lower outer break contacts of relay Ill to conductor H3. Thisdisconnection of battery H6 makes the district junctor test busy to thesender link and control circuit on subsequent calls. Hold magnet 903 ofthe sender link and control circuit also connects ground to conductor-22, which is extended through upper outer break contacts of relay I23and resistance I24 to sleeve conductor I25, thereby supplying aholdingground for the line link hold magnets IN and M6, while thesender bill]is connected to the district junctor circuit.

While the connection is being established from the calling line Hill tothesender circuit 990 the subscriber sender link and control circuit ofFig. 9 is momentarily connected to sender circuit liiil and during thismomentary interval sender circuit 968 is furnished with the class ofservice information of line I09) and also is informed of the number ofthe district link and connector frarneassociated with the districtjunctor circuit to which sender $00 is connected. The line link andgroup control circuit and the subscriber sender link and control circuitare used only momentarily to connect line Itll to an idle districtjunctor circuit and a subscriber sender circuit and are then released toserve other calls but the connections through the cross-bar switchesIiII, I02, Bill and 902 which these circuits' have established are heldby the subscriber sender circuit Bill! under control of the callingsubscriber. After the ofiice code has been dialed, sender 900 connectsto "the originating marker circuit 206, by means of a connector circuit905, over a group of conductors represented by the broken line 906. Thesender circuit Bill! registers in the marker circuit 2% the ofiice code,the class of service information of the calling line IM, and the numberof the district link and connector frame serving the district junctorcircuit involved in the call. The marker 2M then furnishes the sender 9%with the necessary information which it requires to control the progressof the call. Marker 200 then selects an office link and connector frameon which the desired trunk 2%, leading to the called destination,appears, connects itself thereto and also to the district link andconnector frame that is associated with the district junctor circuitinvolved in the call. After this has been successfully accomplished,marker 26!) connects ground to a conductor which is extended throughconnector 9535, sender 9M. and the sender link circuit consisting ofswitches and 982 to conductor I13, thereby operating district ,iunctorrelay IZ'I'. Relay I21 in operating connects ground with its uppernext-to-innermcst contacts to conductor I28, thereby operating selectmagnet 205 of the primary switch 2!!! of the district link and connectorframe serving the district junctor of Fig. 1, and connects ground withits lower inner contacts to conductor 83L thereby operating relay '207,which is common to a group of district junctors served by the primaryswitch represented by the box 28!. The operation of relay 2E3! extendsconductors E29, I383, I3I. I32 and 209 through contacts of a markerconnector relay to the marker circuit 211!) selected for handling thecall being established. This connector relay which is not shown, beingindicated only by broken lines, is individualto the marker circuit 208and is operated each time that marker 26!) is selected for service inestablishing a connection to the district frame represented by Fig. 2.Conductor I29 is used by marker tilt to determine when the primaryswitch 25H has operated from ground supplied by the marker overconductor 269. This is effected, by the extension of the aforesaidground through lowermost primary switch contacts associated with magnet2&8, over conductor I'M, through upper outermost make contacts of relayI21, over conductor I29, through upper neXt-to-outermost make contactsof relay ZIJI, and contacts of the aforesaid marker connector relay, notshown, to

marker 2%. 7 Conductor I30 is grounded by marker ilt through uppernext-to-innermost contacts of relay 201, to operate relay I33, throughupper innermost contacts of relay I27, for calls to an operator.Conductor ii is used by the marker Zi'idto hold relay IZ'I operated,through its lower innermost contacts, until the marker 2% releases, ashereinafter described, and conductor I32 through lower outermost makecontacts of relay I2? to give the sender 9% a trouble release signal ifa trouble condition has been encountered by marker 2% in establishingthe connection. If relay I33 is operated it will look through its lowerinnermost make contacts to ground supplied by sender 900 over conductorMarker Zllil now establishes the connection through the district andomce switches to trunk 286. Select magnet 2H. of secondary districtswitch 202 is operated by ground on the lower outer contacts of relayZII'I. Select magnet 252 of the primary office switch 203 is operated byground on the upper contacts of relay 2I3,'and select magnet 2M of thesecondary switch by ground on the contacts of relay M5, both of whichrelays are operated by marker mill. The

- link between the secondary district primary ofllce switches isestablished when relay BIS is operated by marker 20!] and operates holdma nets 2 I I and 2|! from ground over conductor 236. The link betweenthe primary and secondary switches of the office frame is completed,when. hold magnet H8 is operated from ground in the marker through lowercontacts of relay 2L3.

After the marker Hill has established connection with the trunk 286 asbefore described, it releases relay IEI by removing ground from thewinding of relay 2B1. Relay IZ'I releases and closes the sleeveconductor l'l l through to ground on the upper inner make contacts ofrelay Ill. Marker 20!] tests for this ground and if it finds this grounddisconnects. Relay II'I was operated over conductor Ilfi when the senderlink and control circuit connected sender 905! to the district junctorof Fig. 1. Relay I21 in releasing opens conductors I28, I29, I3Il, I3Iand I32 to the district link and connector circuit and con nectsconductor I with its lower outermost break contacts, to the winding ofrelay I36 so that the sender can operate this relay later.

When the marker has established connection to the outgoing trunk 286,sender 9% then cooperates with the incoming apparatus of Fig. 3 tocomplete the call to the line of the called station 3%. In connectionwith this incoming paratus a terminating sender and terminating marker,not shown by Fig. 3, are provided. As soon as the connection to trunk 2%is established, a circuit is closed for operating relay 3%, throughbreak contacts of relay 3%, over the established connection and overconductors I46 and M5 extending into the subscriber sender 955. The

operationof relay 305 at first closes a start leads not shown, thatcauses the terminating sender aforesaid to be connected. After this thet.ermi-- nating sender receives from sender 900 the necessaryinformation for completing in cooperation with the aforesaid terminatingmarker the con-r nection to the line of the called station 306.

After sender 980 has completed its functions in establishing theconnection, as above outlined, it connects ground to conductor I35 tooperate relay I36 through lower outermost'break contacts of relay I27.When relay I36 operates it;

locks under control of relay I12 in a circuit from.

battery through the winding of relay I36, upper innermost break contactsof relay I12 to ground on the upper next-to-innermost contacts of relayI36. Relay I36 in operating closes the transmission circuit to stationI83. This may be traced from conductor IIII, through upper outermostbreak contacts of relay I I2, upper next-to-outer.

most makecontacts of relay I36, upper next-tooutermost break contacts ofrelay I72, condenser I37, lower middle make contacts ofrelay I36; andlower outermost break contacts of relay" I12 to conductor I38; also fromconductor I I I,

through lower innermost break contacts of relay IIZ, lowernext-to-innermost make contacts of I00. For this purpose ground issupplied through the left winding of relay MI, upper neXt-to-innermostbreak contacts of relay M2 to junction polnt I 42; battery is suppliedthrough the right winding of relay MI, lower next-to-innermost breakcontacts of relay H2 to junction point I43.

After sender circuit 9% has completed its func 'tions and has operatedrelay I36 over conductor I35 as before stated, it releases. This causesthe cross-bar switches 9M and 9M of the sender link circuit of Fig. 9 tobe released which opens the connection of conductors H4, H5, I34, I22,I13, I44, I45 and I35. The established connection is now placed undercontrol of the district junctor circuit of Fig. 1. The connection isheld under control of relay III which remains operated provided the,calling subscriber station I03 is still connected to the line causingthe operation of relay MI over the line loop. Relay I4! operated holdsrelay II I operated in a circuit that is traced from ground on the upperoutermost contacts of relay II'I, operated contacts of relay I M upperneXt-to-innermost break contacts of relay I'IZ, through winding of relayII! to battery.

After the connection to the trunk 206 has been 3 established, a-circuitis completed for operating the bridged impedance relay 365 of theincoming trunk circuit over the loop extending to the calling districtjunctor of Fig. 1. This may be traced through the windings of relay 365,upper and lower break contacts of the reversing relay 3%,

over trunk 2%, contacts of the cross-bar switches EM, 293, 262, 2M, overconductors I49 and I38, outermost break contacts of relay I12, upperoutermost make contacts, and lower middle make contacts of relay I36,winding of polarized relay Its and retardation coil Ml and lower inneroperated make contacts of relay III. Relay 3B5,

operates in this circuit, but polarlzed relay 146 does not operate atthis time.

When the called subscriber of station 304 answers, a circuit is closedfor operating the bridged impedance relay 301, which maybe traced. frombattery and ground through the windings of relay 301 over the tip andring conductors and contacts of the cross-bar switches 300 and SM of theincoming link circuit and of the cross-bar switches 302 and 303 of theline link circuit to the line leading to the called station 304. Relay301' in operating closes an obvious circuit for operating the reversingrelay 306, which in operating reverses battery and ground over trunk206, thereby causing polarized relay I46 of the district junctor circuitof Fig. 1 to operate. Re-' lay I46 in operating connects ground to thearmature of interrupter I48, through the upper innermost breakcontacts'of relay I33. When interrupter I48 connects ground to the'lowerwinding of relay I23, relay I23 operates and locks to the operatingground through its lower inner make contacts. After a convenientpredetermined short interval, saytwo seconds, interrupter I48'closes acircuit for operating a charge relay I49, through a circuit from batterythrough the winding of relay I49, lower outermost break contacts ofrelays H2 and I50, off-normal contacts -I69 of interrupter cam I5I,upper outermost outermost break contacts of relay IIZ to ground on thelower outermost operatedcontacts of relay I 49; (1)) partially preparesa path for starting an automatic release circuit, to be hereinafterdescribed by connecting to interrupter I54, with its upper outermostmake contacts the break contacts of the polarized relay I46; (0)partially prepares a path, by closing its upper next-toinnermostcontacts, for operating relay I12 by connecting the winding of relay I12to the upper contacts of relay I55; (d) provides an auxiliary holdingcircuit for relay I36 which is required when the automatic. releasecircuit arrangement releases the district junctor circuit by operatingrelay I12, this holding circuit extending from battery through thewinding of relay I36, lower outermost break contacts of relay I21 toground on the upper middle contacts of relay I49; (6) partially closes,with its upperv innermost make contacts, the circuit for operatingmessage register I56; (1) opens with its lower innermost break contactsthe tip conductor of the trunk towardy relay I12 so the trunk circuitwill start to release when relay I12 is operated by the automaticrelease circuit; (9) connects ground, with its lower, next-to-innermostmake contacts to conductor I51 to be used later by the coin controlcircuit as a signal to collect the coin deposited in the coin box I04associated with the station I03, (h) closes a circuit for operatingthe'magnet I58 tostarttiming the call. This circuit is traced frombattery through the winding of magnet I58, lower next-to-oute'rmost makecontacts of relay I49, upper innermost break conwhen relay II1 releases.

tacts of "relay H2 "to ground on the upper outer make contacts of relayII1.

It is now in order to describe the operation whereby a coin deposited incoinbox I04 is collected or returned; or an operator is summoned, tomonitor on an overtime call,'or in response to a failure of the callingparty to deposit a coin or in response to a stuck coincondition;

' The collection of the deposited coin due to the disconnection of thecallingparty, prior-to the expiration of the time limit will now bediscussed. When the calling party-at station I03 disconnects, relay MIreleases, which. in turn releases relay lI1. Relay I46 releasesreleasing relay i253 when the called party disconnects or When relay II1releases it operates relay I20 in a circuittraced from ground throughthe lower winding of relay S20, upper middle make contacts of relaylilt, upper neXt-to-cutermost contacts of charge relay I SQ, loweroutermost break contacts of relay I2I, lowerouter break contacts ofrelay II I, upper outermost break contacts of relay I2 I, lower next-tooutermost' make contacts of relay I35, upper innermost contacts of relayEZI to battery through resistance I59. (a) locks through its lowerinnermost contacts and upper innermost break contacts of relay l2} 1 tobattery through resistance E59; (b) connects ground with its lowermiddle contacts, through lower middle break contacts of relay I2! tostart Relay I20 operated furnishes "a holding circuit for relay I36,this holding circuit being traced from ground on the lower outermostmake contacts of relay 520,

through upper outermost break contacts of re-, lay I23, and upperinnermost make contacts and winding of relay I36 to battery. 6

' When ground. is connected to start conductor I60, as aforesaid, thelink and control circuit of Fig. 5 functions and causes a coin controlcircuit, which is shown by Figs. 6, '1 and 8, tobe connected. Fig. 5. isnot apart of this invention, is shown only in skeleton form and only tofacilitate the description of this invention. Link and control circuitsof the type required for use with this invention are so designed that,when summoned for service, an idle link from a group of links isselected, and the selected link then selects an idle coin-controlcircuit from a group.

of coin-control circuits. With these selections made, the requiredconnection between coin-control circuit and district junctor is nextestablished. When ground is connected to start conductor I60, relay 502operates throughits upper winding and looks through its lower winding toground on the lowermost contacts of relay Ground on the upper outercontacts of relay 502 operates primary select magnet 504 of crossbarswitch 500, and ground on the upper inner contacts operates relay 505,through upper break contacts of relay 506. Relay 505 looks through itslower inner contacts to ground on the lower inner break contactsof relay503, with its upper inner contacts. it operates select magnet 501 ofsecondary cross-bar switch 50E, and with its upper outer contacts relay50B. Relay 508 connects ground to the multipled windings of primary holdmagnets 509 and 540, and secondary hold magnets 5! I and 5I2 and thesemagnets operate causing cross-bar switches 500 and 5M to controlconductors 5I5, 5M, 5, 525', 5I5, SIS; M8 and 525, respectively.

When the link and control circuit of Fig. 5 establishes a connection, asbefore described, re-

' lay 505 connects ground with its lower outer contacts to conductor522, thereby operating relay 554. Relay 554 operated (a) connects thewinding of relay 555, with its upper outermost front contacts toconductor 005, so that this relay may operate if ground is connected tothis conductor by a district junctor that requires overtime monitoringservice, as will be hereinafter described; (b) connects together, withits upper next-toinnermost contacts conductors 52I and 526, therebyoperating relay 521 from the operating ground supplied by relay 503through switch contacts 528; (c) connects the upper winding of relay656, through its upper neXt-to-outermost make contacts, over conductor520 to the Winding of release relay 503; (d) partially prepares,'withitslower 'next-to-outermost make contacts, a circuit for operating relay551 over conductor 524; (e) connects with its lower outermost makecontacts, the winding of relay 558 to conductor 525, so that this relaymay operate for coin-return service as will be hereinafter. described.

Assuming that ground has been connected to conductor 4 57 by the actionof the district junctor circuit of Fig. has before described, therebyestablishing the condition for coin collection, relay 659 operates in acircuit from battery through its I winding, lower middle break contactsof relay 051,

lower outermost break contacts of relay 050, over conductor 5H, throughassociated contacts 10f cross-bar switches 583i and 500 to said groundon conductor I51. Relay 559 in operating, operates relay I in a circuitfrom ground on the upper middle make contacts of relay 059, throughlower innermost break contacts of relay 560 to battery through thewinding of relay 06 I. Relay Gtl in operating, connects ground toconductor 5! in a circuit traced from ground on the upper inner makecontacts of relay 56L through'lower innermost break contacts of relay551. This operates relay 505, which connects ground with its lowercontacts to conductor 523, operating thereby relay 655 in a circuit frombattery throughv its lower winding, lower innermost make contacts ofrelay 555 to said ground on conductor 523. Relay 05I also operates relay062 in a circuit from battery through the winding of .relay 662, lowermake contacts of relay 50 I lower outermost break contacts of relay 554,when this relay releases as hereinafter described, over conductor 525,through apparatus of Fig. 5, over conductor I55, upper middle breakcontacts of relay I50, to ground on the lower outermost break contactsof relay I59, when this relay releases after its locking circuit isopened by the operation of relay 9 I2, as hereinafter described. Relay555 in operating supplements the operating ground for relay with aholding ground connected through the upper innermost contacts of relay556 and lower innermost break contacts of relay 550. This is necessaryto avoid premature disconnection of the coin-control circuit inconnection with overtime monitoring as will be discussed later. Relay556 also connects ground, with its upper middle contacts to conductor5I5 and thence through upper next-tooutermost break contacts of relay802, break contacts of jack 853 and winding of the time signal relay 800to battery. The operation of this latter relay will be discussedhereinafter. Relay 556 also connects ground to conductor 519, through acircuit tracedfrom ground on the lower nextto-innermost operated makecontacts of'relay i, lower outermost contacts of relay 656 to conductor5I9. Relay 556 also closes a holding circuit for relay 559 which istraced from battery through the winding and lower innermostoperatedcontacts of relay 559 to ground on the lower neXt-to-innermostmake contacts of relay 556.

Relay 555 also partially prepares, with its lower innermost contacts acircuit for operating relay When the link circuit has completed itsfunctions as evidenced by the presence of ground on v sleeve conductor52I, it operates relay 521 over make contacts of relay 554 to saidground on conductor 52L Relay 52! connects ground to conductor 520,which ground is extended through the lower next-to-outermost makecontacts of relay 554, lower innermost make contacts of relay 655 tobattery through the winding'of relay 651 which operates. Relay 051operated (11) connects conductor 526, through upper next to innermost'ground to conductor MS, with its .upper outer energizes the upperwinding of relay 556 in a' circuit from battery through the upperwinding of relay 655,upper next-to-innermost make con-;

tacts of relay E5! to ground on the lower next-toe;

innermost contacts of relay 655, this same ground also operating linkrelease relay 503, through upper next-to-outermost make contacts ofrelay 855 over release lead 520; (e) partially prepares the operatingcircuit for relay H2 byconnecting ground from the upper outermost makecontacts.

of relay 559, through lower outermost make contacts of relay 651 to theupper innermost break contacts of relay 654, which connect to the winding of relay H2, over conductor 613. Relay'503 in operating releasesrelay 505, causing the re-- lease of relay 508, and secondary selectmagnet 56?. As before stated, hold magnets 509, '5I0, M I and 512 areheld by ground on conductor 52L When ground is connected to the sleeveconductor I54, a circuit is closed for holding relay I20 of Fig. 1through its upper winding and for operating relay I'2I through its lowerinnermost normally closed continuity contacts. Relay IZI looks throughits lower innermost make contacts to ground-on the upper middle makecontacts of relay I20, and'disconnects with its lower middle breakcontacts" the start lead I00 from'groun'd on I 7 Relay- 502 accordinglyreleases dueto the opening of the the lower middle contacts of relayI20.

locking circuit through its lower winding; when relay 503 operates anddeenergizes the primary select magnet 504.

The release of relay 505, as before described,- removes ground fromconductor 522 thereby causing the release of relay 554. Relay554disconnects conductors 526', 520 and 524 and transfers conductor 523from the lower winding of relay 550 to conductor 0H5 so that the alarmcircuit will function if conductor 523 is grounded for an abnormallength of time. The release of relay 654 also" closes the circuit foroperating re-- I lay H2, which circuit was traced hereinbefore;

For coin-collect calls, relay 659 is operated as described hereinbefore,andholds to ground on the lower, next-to-innermost contacts of relay656.' Relay H2 operated closes the holding circuit for relay 663, whichis traced from ground on the upper outermost make contacts of relay H2,over conductor 638 to the lower innermost contacts of relay 663; alsothe holding circuit for relay H3 which is traced from ground on theupper middle make contacts of relay H2 to the upper innermost makecontacts of relay H4.

Relay "H2 connects ground to interrupter Hl over av circuit frominterrupter HI, through lower innermost make contacts of relay H2,

over conductor 65!), through lower outermost break contacts of relay892, over conductor. 613,

to ground on the upper outermost make contacts of relay 659. At thefirst ground closure of interrupter H I, relay H4 operates through itsupper inner normally closed contacts and winding and resistance H6 tobattery and'locks through its upper inner make contacts to ground on theupper middle make contacts of relay 1 l2. Relay H5, is shunted by groundconnected to its winding through its upper inner break contacts and doesnot operateiwith relay H4 at this time. When ground'is removed byinterrupter Hi at the end of the first ground closure, relay H5 operatesin a circuit from battery through resistance HI, winding of relay H5 toground on the upper inner make contacts of relay l M. Relay H5 inoperating operates relay 663 in a circuit that is traced from batterythrough the winding of relay 663, over conductor 653,through lowerinnermost break contacts of relay 805, over conductor 105, through lowerneXt-to-outermost break contacts of relay. H8, lower outer breakcontacts of relay H9,lower inner make'contacts of relay H4 to ground onthe lower make contacts of relay H5. Relay H5 also connects groundthrough its lower make contacts, lower inner make contacts of relay H4,lower outer break contacts of relay H9, upper next to-outer most breakcontacts of relay H3, lower ,outer break contacts of relay 12!), overconductor 649, through upper innermost break contacts of .relays 658and660 to conductor 5l8; thence over conductor 5l8, through the contacts ofcross-bar switches and 550 to" conductor NH and the winding of .relayH2, which operates. Relay 663 operated (a) locks over conductor 538 toground on the upper outermost contacts of relay H2; (b) partiallyprepares a circuit for operating relay H9 over conductor 643 by closingits lower 'middle contacts; (0) connects coin-co1lect battery 664,through resistance lamp 665 and the winding of'relay 566 to conductors545 and 5&6 over the following circuit path: lower outermost operatedcontacts of relay 659, lower neXt-tooutermost break contacts of relay658, upper innermost make contacts of relay 663, over conductor 64!),upper middle break contacts of relay H9, over conductor 631 to thecenter terminal of the primary winding of transformer 5G1, thencethrough theleft section of said winding, upper outermost break contactsof relay 554, over conductor 6M and through the upper innermost breakcontacts of relay H8 to conductor 6m, thence through the upper innermostbreak contacts of relay 668 to conductor 515: the path to conductor 5l6is traced through the right section of the winding of transformer 661overconduc- I calling telephone station H13.

necting, to conductor 516, aforesaid. Conductors M5 and 5% are extendedthrough the apparatus of Fig, 5, over conductors IE2 and 153 through theupper outermost make contacts, and lower innermost make contacts of theoperated relay H2 over the line conductors of the Relay E66 operates inthe circuit, above traced, provided "that a coin N35 has been depositedin the coin box I04, which has thereby connected ground I09 throughcoin-box contacts 168, and the winding of coin magnet Its-to the tipconductor of line Hill, and through the switch contacts of the telephoneof station I03 to the ring conductor of said line. Coin collector magnetI08 is now operated and collects coin I05 in the manner well known inthe telephone art. Relay 666 operated, operates relay (2| over conductor633. Relay [2! operated connects (a) ground to the winding of relay 655,over a circuit traced from the Winding of. relay 56L through lowerinnermost break contacts of relay 6%, over conductor 632, to ground onthe upper innermost make contacts of relay MI; (1)) looks through itslower innermost make contacts, over conductor 528 to ground on the upperoutermost contacts of relay 656; (0) partially prepares a circuitthrough its lower outermost make contacts for operating relay 568. Atthe second closure of the contacts of interrupter H i, relay l M isshunted by ground connected through the upper innermost make contacts ofrelay H5, to the lower terminal of the winding of relay H4. Relay HGreleases, but relay H5 is held operated through the upper inner normallyclosed contacts of relay lid, to ground on interrupter H I. Wheninterrupter H l removes the second application of ground, relay H5releases. Relay H5 released operates relay H9 in a circuit from batterythrough the winding of relay H9, over conductor 643, lower middle makecontacts of relay 553, lower middle break contacts of relay 668, overconductor to ground. on the lower break contacts of relay H5; its uppermiddle break contacts the circuit for the coin-collect battery 564,before traced, thus releasing relay 555; (b) locks to ground on itsupper innermost make contacts over conductor (0) operates relay 855, ifrelay 128 has failed to operate due to the absence of ground H39,because of failure to deposit a coin, or for any other reason.Theoperating circuit for relay 805 is traced from battery through thewinding of relay 855, over conductor EGG, lower innermost break contactsof relay 1 It, upper middle break contacts of relay lZI, lowernextto-innerrnost break contacts of relay H3, lower innermost makecontacts of relay H9, over conductor 648, through upper innermost makecontacts of relay 555, over conductorv 505, to ground on the lowermiddle break contacts of relay 882. If relay I21 has operated, inresponse to the operation of relay 665, as before described, thusindicating the presence of ground at coin box HM, a test is now made todetermine whether the coin box N14 has been satisfactorily cleared, asit normally-should be cleared, by the operation and release of thecoinfmagnet I08. Under this condition, at the beginning of the thirdground closure of interrupter HI, relay H4 operates, but relay H5 isshunted and does not. operate, as hereinbefore described in connectionwith the Relay H9 operated, (a) opens with' 1st I first ground closureof interrupter H I. At the 15 Ti-fend of the third ground closure ofinterrupter l! l, relay lit also operates and now relay 668 is .7operated in a circuit traced from battery through the winding of relay5%, over conductor 6H, through upper next-to-innermost break contacts ofrelay "HS, lower outermost make contacts of relay 'l2l, over conductor535, through upper middle make contacts of relay 662, operated ashereinbefore described, over conductor 644, lower outermost makecontacts of relay H9, lower innermost make contacts of relay M4, toground on the lower make contacts of relay 7 l5. Relay 658 operated (a)partially prepares the circuit for operating relay etc, as will behereinaiter described, by closing its lower middle make contacts; (2))looks to ground on its upper next-to-cuterniost contacts, through uppernextto innermost contacts of relay HS, and lower outermost make contactsof relay 12!; (c) closes a circuit for charging the condensers atstation we, and the line capacity through the winding of relay 659,which circuit may be traced from battery through the winding of relay669, lower innermost make contacts of relay .568, thence over the ringconductor to station Hi3; another path for the tip conductor may betraced by way of the lower innermost break contacts of relay 6% andupper innermost make contacts of relay 663 to said tip conductor. Relay669, even though the coin has been successfully cleared.

due to the capacity charging may operate momentarily, but its contactsare ineffective to operate relay 722 until relay 1M releases at thebeginning of the fourth closure of interrupter ill. Assuming that relay659 does not operate efiectively due to the successful clearing of thecoin, then a circuit is closed for operating release relay 6% which istraced from battery through the winding of relay 65!), upper middlebreak contacts of relay 655, over conductor 62E,

upper outermost break contacts of relay J22,-

over conductor 523, lower middle make contacts of relay $68, overconductor Bill to ground on the lower break contacts of relay H5, whenit releases after the end of the fourth ground closure from interrupterH i. The coin-control circuit is-then released as will be hereinafterdescribed. If, however, relay 659 operates steadily due to a stuck coin,then when relay Hi releases, at the beginning of a fourth ground closurefrom interrupter TH then a circuit is closed for operating relay F22,which circuit may be traced from battery through the winding of relay722, over conductor 623, contacts of relay 859, lower outermost contactsof relay 5%, over conductor 6E9, through upper outer break contacts ofrelay 1.29, lower inner break contacts of relay M4 to ground on thelower make contacts of relay H5. The circuit operation of relays lid andM5 for the beginningof the fourth ground closure is the same as that forthe beginning of the second ground closure hereinbefore discussed. Relay322 operated (a) locks through its lower make contacts, over conductor821 to ground on the upper outermost contacts of relay 663; (b) closesground with its upper innermost contacts, over conductor 622, to thewinding of relay 569, thereby discharging the capacity of the callingsubscriber line to prevent bell tapping when relay see is removed fromconductors E25 and'hifi; (c) closes a circuit for operating relay 885,which is traced from battery through the winding of relay 8&5, overconductor TM, through lower innermost break contacts of relay H3, upperoutermost make contacts of relay I21, and lower contacts of re 1connected to relay "22 to the holding ground lay 122.

The before-given description covers the condi tion, on a coin-collectcall, which exists when a coin is found in the coin box and iseithercleared or not cleared. The condition, when acoin is not found, will nowbe discussed; If no coin is found, relay i556 fails to operate andlike-,- 3

wise relay l2! When relay ll 9 operates,.a circuit is also closed foroperating relay. 895, which is traced from battery through thewindingyof relay 8%, over conductor 1M, through lower innermost breakcontacts of relay i-lky'upper, '7

middle break contacts of relay 22!, lower nextto-innerrnost breakcontacts of relay H3, lower tacts of relay $59, over conductor iiiiii toground on the lower middle break'contacts of relay 802.

Relay 855 operated releases relay 865, which =op- 1 era-ted when relay66! operated. The operating circuit for relay 806 is traced fromubattery.

through the winding of relay SWLIIOWQI outer I most break contacts ofrelay 86.5 over conductor 693 to ground on the upper outermost contactsof relay 83!. Relaytlfli operated, with itsdower innermost breakcontacts removes ground from Y conductor EM and opens the operatingcircuit of relay N2 of the district junctor circuit of Fig. 1. RelaySilt is slow to release to permit relay M2 to release before relay H8 isoperated to avoid clicks at the calling station. .ReIay'HB is operatedfrom battery through its winding, over conductor 768, through rightouteribrea'k contacts of relay 8%, upper innermost makecontacts of relay895, over conductor 6.00 to ground on the upper outermost break contactsfoi relay 666. Relay H8 operated (a) connects transmission conductorstilt and 5M by means of its outermost make-contacts to conductors 1% andllltextending to ,theline-splitting jack 801 but these conductors arenot usedfor jstuck'coin conditions; (1)) connects-conductors'di!) and M2to conductors 1B! and 1%, respectively, extendi ing to the inner makecontacts of relay 862; (a) partially prepares the operating circuit forrelay 802 by connecting ground, with its upper nexttoouterrnost makecontacts, to conductor 8-H;

'(cl) releases relay 668 byopening its operating circuit with its uppernext-to-innermost break contacts; (e) partially prepares a circuit forlighting lamp Wit by connecting battery through itslowernext-to-innermost contacts over'conduotor 789', through upperoutermost break con tacts of relay 8%, over conductor 6M thrbugh,

outer lower make contacts of relay H4, over conductor 852, through uppermiddle break con-,

tacts of relay 6%, upper outermost break contacts of relay 668, throughlower innermost make contacts of relay 6-152, over conductor 645,,and

through lamp 895] to ground. Due to the interrupted operation of relay lM, lamp will flash.

This is a signal to the operator thatthe coincontrol circuit has failedona coin-collect'call which may be due either to no coin in the coinbox, or to failure to collect, assuming that the coin is present.Accordingly, the plug of. the cord circuit 837 is inserted into jack8519, associated with lamp 800, operating relay 832 over the,

sleeve circuit and extinguishing lamp 899. .The

operator will now endeavor'to collect the coin by 1 operating coin,collectkey 8H2, which will connect coin-collect battery 833 to thetip'and ring of the line. If a coinis" present pilot relay M5 ground onconductor 525..

will, operate, lighting the pilot lamp 8I6; if no coin is present relay8I5 will not operate and lamp 8I6 remains unlighted. If lamp 8I6 lights,the operator will close the circuit a second time, and if it remainslighted it is an indication that the coin is stuck and cannot becollected. Relay 802 operated also (a) connects condenser 8I'I acrossthe tip and ring conductors under control of relay 806; (1)) holdsrelays H8 operated to ground through its upper next-to-innermostcontacts; operates relay H3 over conductor I28 to ground on its lowernext-to-innermost make contacts; (d) opens, with its uppernext-to-outermost break contacts the circuit of the alarm relay 804 sothat an alarm will not be unnecessarily given if the operator keeps theplug of the cord circuit 831 in jack 809 for a long interval. Thepurpose of relay M3 for the type of call being described is to guardagainst premature disconnection should the operator inad-H vertentlyplug into the release jack BIB instead of into the monitoring jack 809.Relay I I3 operated (a) locks through its uppernext-toinnermost makecontacts to ground on the upper innermost contacts of relay I I2; (b)releases relay 805 by opening the operating circuit hereinbefore tracedand thereby operates relay 806 over conductor 603; (0) partiallyprepares the circuit for operating release relay 660 in a circuit frombattery through the winding of relay 660, upper outermost make contactsof relay 662, overconductor 608, upper innermost make contacts of relayH3, over conductor I30 to ground on the left contacts of relay 834,which operates when the operator inserts a plug into release jack 8I0;

(d) closes a holding circuit for relay H8, which may be traced frombattery through the winding of relay ,II8, lower outermost makecontacts'of relay H3, over conductor 629, through lower outermost makecontacts of relay 662, over conductor 601, through next-to-outermostmake contacts of relay H8 to ground. When the operator removes the plugfrom jack 809, relay 802 releases and relights lamp 800 until theoperator inserts the plug into release jack 810, which operates relay,834. Relay 834 operated, operates release relay 660 over the circuithereinbefore traced and connectsground to conductor 605, which connectswith conductor I9 extending into the link and control-circuit of Fig. 5,there by keeping relay 506 operated and causing the coin-control circuitto be inaccessible to other district junctors requiring service, untilthe operator removes the plug of cord circuit 831 from jack 3H). 7 fromits connectionwith the district junctor circuit of Fig. l whenrelay 660operates. This feature will be described in detail hereinafter.

The operation of the system for coin collection after thecalling partyhas disconnected has been discussed hereinbefore. The operation for coinreturn, after. disconnection, will now be described. Assuming, thatconnection of the coin-control circuit of Figs. 6, 7 and 8 has beenestablished with the district junctor circuit of Fig. l ashereinbeforedescribed, ground on the lower outermost break contacts of relay I49will v be connected through upper middle break contacts of relay I50 toconductor I65, thence through switch contacts ofFig. '5 to conductor525. Coin-return relay 658. is thenv operated from battery through thewinding and the lower outermost make contacts'of relay 654 to said Relay658 operated (a). :connectscoin-retrirn battery .610, through Thecoin-control circuit is released resistancelamp 6', lower middle makecontacts 7 .of relay 658, and thence over the circuit path beforedescribed for coin collect to the coin box J04 ofthe calling station;(b) operates from ground on its upper outermost contacts, over conductor633, relay 'I2I; (c) looks through its lower innermost contacts toground on the contacts of relay 655, as did relay 659 in the beforegivendescription; (12) operates relay "H2 from ground on'its lower outermostcontacts, over the path previously traced for operation by relay 559.For an oflicial or free call, the completing trunk, not shown, isarranged so that relay I46 and relay I49 do not operate and consequentlythe circuits function as for an incompleted call.

The operation of coin-return relay 658, as before described, causes thecoin at coin box I04 to be returned, the circuits functioning in amanerator, observing the steadily lighted lamp 800,

now knows that the coin should be returned, and accordingly operatesreturn key- 8I3.. If there is a coin present relay 8M operates andlights pilot lamp 8| 6; if the coin clears then lamp 8I6 is not lightedon the second attempt, but if lamp BIG 1 is relighted, this indicatesthat the coin is stuck and cannot be returned.

The operation of the system will now be discussed for the condition,whereby after the expiration of a predetermined time interval followingthe establishment of the conversational con nection between calling andcalled parties, the deposited coin is automatically collected duringconversation anda warning tone is connected to the line to indicate thatthe expiration of the time limit is approaching. It has been foundconvenient to collect the coin at the end of approximately four andone-half minutes, that is, one-half minute before the end of afive-minute period covered by the initial coin deposit. It is to beunderstood, however, that any other time interval that may be desiredcan be used. At the. end of this five-minute period, if no additionalcoin has been deposited, an overtime monitoring operator is called into, supervise the connection.

Let it be assumed now that the called party has answered and that thecams I5I, I52 and I53 have begun. to time the call. As soon as thetiming device moves off-normal, normally closed contacts I69 open. Atthe end of 265 seconds, pick-up contacts I'II close and thereby providea circuit for holding operated rotary magnet 458, after the charge relayI49 releases, as will be described hereinafter. that is, at theexpiration of about four and onehalf minutes, contacts I close, thusoperating .relay I20 over a circuit traced from ground through the lowerwinding of relay I20 and contacts I'II] to battery through resistanceI59. Relay I20 operates and then operates relay I50 in a circuit frombattery through the winding of relay I50, upper innermost, make contactsof relayv I20, loweroutermost contacts of relay I36,

About five seconds later,

to ground through the upper outer contacts of relay I I1. Relay I20operated (a) connects battery II8 through resistance H9, upper outermostmake contacts of relay I20, upper innermost make contacts of relay I49to line register I56, through corresponding contacts of the line linkcross-bar switches IOI and I02, and register I56 operates to indicatethe completion of a call over its associated line; (b) partiallyprepares with its upper middle make contacts a ground connection to holdrelay I2I operated, when this relay subsequently operates; (c) locksthrough its lower winding, lower innermost make contacts, and upperinnermost break contacts of relay I2I to battery through resistance I59;(d) connects ground, with its lower middle make contacts, through lowermiddle break contacts of relay I2I to start conductor I60 to summon acoin-control circuit; (e) provides an auxiliary holding ground for relayI36 which is traced from ground on the lower outermost make contacts ofrelay I20, through lower and upper innermost make contacts and windingof relay I36 to battery. This has no useful function at this time.

When the connection to the coin-control circuit is established ashereinbefore described in connection with the operation of the systemfor coin control after the calling party disconnects, relay I2I operatesand the coin-control circuit receives a signal over conductor I57 tocollect the coin. When this signal is received the coincontrol circuitfunctions, as before described, except that now relay 662 is notoperated, since there is no ground on conductor 525 because the callingparty has not disconnected. With relay 662 not operated, a warning tonewill be superimposed on the line conductors 5I5 and 5I6 through thewindings of transformer 66?. This tone is produced by batteryinterruptions furnished by the interrupter 6'14 and transmitted throughtransformer 612, lower middle break contacts of relay 662, lower middlemake contactsto the coin-control circuit path before traced.

When relay H6 operates, as hereinbefore described, it operates releaserelay 660, provided a coinhas been found in the coin box- I04, in acircuit from battery through the winding of relay 660, through upperoutermost break contacts of relay 662, over conductor 64! through lowermiddle make contactsof relay 'I2I, lower innermost make contacts ofrelay H6, over conductor 648, upper innermost contacts of relay 659,over conductor 606 to ground on the lower middle break contacts of relay802. Relay 660 operating, releases the coin-control circuit, ashereinafter to be described. The stuck coin test, using relay 669, whichtest was hereinbefore described, is not made at this time, so as toavoid interrupting conversation. This test is made after disconnection.However, if the coin-control circuitfinds that no coin has beendeposited as evidenced by the non-operation of relay 666 andconsequently of relay 12! then a circuit is closed for immediatelyflashing the overtimemonitoring lamp 80L This circuit is traced fromground through lamp 80I, over conductor 64?, lower innermost breakcontacts of relay 662, thence over the circuit before traced forcoin-control lamp 600'. When the operator observes the flashing lamp80!, the plug of the cord circuit 8 is insert-ed in the overtimemonitoring jack 806, relay 002 operates and the circuit functions asbefore described. Relay H2 of the district junctor circuit is operatedas before described in connection with a stuck coin condition and thecallingline is circuit for, relay connected to conductors I62 and I63,The called subscriber is bridged across the connection by means ofconductors I66 and I67.

the cord circuit collect key 8I2.

The operation of the system for overtime monitoring by an operator willnow be described.

For this con- I dition, the operator requests the deposit of a coinwhich she immediately collects by operation off5 When the test indicatesat the end of the five- I minute period that a coin has been deposited,the

coin-control circuit is released and conversation through the districtjunctor is-uninterrupted. If no coin is found then the monitoringoperator is signaled with a steadily lighted lamp, and the operator uponanswering the signal requests that I the calling subscriber deposit acoin in payment for the succeeding overtime interval or permits thecalling party to disconnect if the conversation is to be terminated.

connects, the operator removes the cord circuit plug from the monitoringjack and the coin- If the calling party maintains that a coin has beendeposited or disnects a second time, the coin-control circuit repeatsthe procedure of verifying disconnection or the presence of a coin atthe calling station. When a coin is found present, the coin-controlcircuit dismisses the district junctor. If disconnection is detected,the coin control circuit is required to proceed with coin-return serviceto insure that the coin-box station has been properly cleared.

' The operation of the system for overtime monitoring will now bediscussed in detail. Let it be assumed that the district junctor circuitshown on Fig. 1 has'cooperated with the coin-control circuit of Figs. 6,7, 8 to collect, at theend of the four and one-half minute period, thecoin contacts of relay Ill. Relay I50 also remains net I58. A smallinterval before the timing device completes a cycle of five minutescontacts- I69 reclose', and. a circuit is closed for operating relayI20, which relay released when ground wasv removed from conductor I64following the dismissal of the coin-control circuit after the four andone-half minute period. The I20 is. traced from ground through its lowerwinding, lower outermost make contacts of relay I50, contacts I69, upperoutermost make contacts of. relay I50,land -resistance I56 to battery.The operation of relay I20 sumtery through thewinding of relay I50,upper innermost make tcontactsof relay 1.20,. lower ."outermost contactsof relayrI36 to ground on tor I8 causes relay II2 of the district'unctor the upper outermost contacts of relay 1. v Mag- -net I58 is heldto the same ground through the lower innermost contacts of. relay I50,and the timing device continues to function. However, the actual timingof the callwill not be resumed until the coin-control circuit isreleased; When I this occurs the holding ground on conductor I64 isremoved,and relay I20 releases, thereby releasing relay I60. The releaseof relay I50 opens the operating circuit of magnet I58, which is soconstructed that it now immediately restores .to normal and the timingof the call isresum'ed. .If, however, assuming an extremecondition,xthat the coin control circuit should beheld until contacts.III reclose, thereby maintaining the operation of magnet I58, thedistrict junctor must then wait until contacts IH open, that is, untilthe timing mechanism has restored to normal, before timing is resumed.As herein before stated, the presenceof. ground on con-' 604, throughupper innermost break contacts of relay H8, over conductor filll throughupper innermost breakcontacts of relay 668 to aforementioned conductor5I5. Relay 655 looks, when relay 656 operates, in a circuit through itslower middle make contacts,.upper innermost break contacts ofrelay 662to ground on the lower next-to-outermost make contactslof relay 656.;

After the link and control circuit of Fig. 5 has operated relay 65Iitreleases and causes the release of relay 654 as before described. When.relay 654 releases relay H2 operates from ground on the upperneXt-to-outermost contacts of relay 665, over conductor 650, throughlower outermost .break contacts of relay 802,.over conductor 6I3 throughlower outermost make contacts of relay 651, upper innermost breakcontacts of relay 654, over conductor Y613 and through winding of relayII2 to battery. Relay H2 operated connects ground on the uppernext-to-outermost contacts of relay 655, over conductor 650, throughlower innermost contacts of relay H2 to interrupter II I; (b) connectslocking groundw'ith. is

upper outermost contacts, over conductor 638, -to the lower innermostmake contacts of relay 663, and with its upper middle contacts to theupper inner make contacts of relay I I4; (0) connects ground to ringconductor 5I4 to guard against clicks to the subscribers when thetrans-, mission circuit of the district junctor circuit is interrupted'to permit testing the calling coinstation for the presence of theyovertimedeposit. This circuit is traced from conductor 5I4, throughlower outermost break contacts ofrelay H8, through lower middle makecontacts of relay II2,"over conductor H0, through upper innermost breakcontacts of relay 805, over cone =ductor 600 to ground on the upperoutermost break contacts of relay 660. Relays I I4 and H5 now operateand release in response to ground interruptions furnished by interrupterHI. When relay H4 operates, it operates relay 663.

and connects ground to conductor .5I8, over cirground closure frominterrupter II I.

cults vh'ereinbefore traced. Ground on conducto operate, which connectsthe calling station to conductors I62 and I63 extending to thecoincontrol circuit. Relay 663 operated operates relay 660 in a circuitfrom battery through the winding of relay 668, over conductor .6I I,through upper next-to-inn'ermost break contacts of relay H8, throughlower outermost break contacts .of relay I2I, over conductor 636,through upper next-to-outermost make contacts of relay 663 to the sameground that. is holding relay 655. Relay663 operated also partiallyprepares a circonductor 643, through upper and lower next-. to-innermostcontacts of relay 663,: over conductor 624,,to the open upper middlemake contacts of relay 805, thence over conductor 63I, through relay 660by closing its lower middle make contacts; (b) closes the circuit forcharging the station condensers and the capacity of the calling linethrough the winding of relay 669 which has its contacts made ineffectivefor a short [interval in order to guard against false operation of relayI22 on line surges; (c) prepares a circuit, for operating relay I22 if acoin is present in coin box I06, all of which has been described indetail in connection with operation for stuck coin conditions. If relay669 should operate on any line surges at this time, it should releasebefore its contacts are made effective when relay H4 releases at thebeginning of the second ground closure from interrupter iii. If a coinhas been deposited, relay 669 will operate as soon as relay 66Boperates, so that when relay II4 releases, relay I22 will operate.immediately. Relay I22 operated (a) connects ground to ring conductor5I6, the circuit being traced ,from ground on the upper innermostcontacts of; relay I22, over conductor 622 and through lower innermostmake contacts of relay 668 to conductor 5I6; this prevents bell tappingon party coin lines when relay 669 is disconnected fromthe calling line;(b) operates release relay 660 over conductor 630, throughupperoutermost .8 aswill be hereinafter described. If a coin has not beendeposited relay 660, and consequently relay I22, will not be operatedwhen the contacts of relay 669 are made effective when relay II Ireleases at the beginning of the second When rolay H5 releases at theend of the second ground closure from interrupter III, a, circuit isclosed for operating relay 805 which is traced from groundv on the lowerbreak contacts of relay H5,-

over conductor I04and through winding of re- .lay605 to battery. Relay,805 looks toground in ,cuit for operating relay H0. This is traced frombatterythrough the winding of relay H9, over

